Behavior of Cu(P) and Oxygen Free High Conductivity Cu Anodes under Electrodeposition Conditions

Films formed on Cu(P) (with 0.1 atom percent P) and oxygen free high conductivity Cu anodes in electroplating solutions were studied by a newly developed gravimetric technique, electrochemical methods, x-ray photoelectron spectroscopy, and x-ray absorption spectroscopy. The black film formed on Cu(P) in Cl^− -containing solutions was found to resemble a porous sponge composed of CuCl but laden with concentrated CuSO_4 solution. The gravimetric experiments show that the difference between the buoyancy-corrected measured mass change and the charge-equivalent mass change has two components: a reversible part that comes and goes as the current is turned on and off, and an irreversible part that remains on the surface and increases in mass with time as dissolution proceeds. The reversible part of the mass change arises from the weight of the diffusion layer. The irreversible part results from the anodic film, which increases linearly in mass with charge density but at a rate that is independent of current density. P inhibits the disproportionation of Cu^+1 that results in the poorly adherent anodic film that forms on OFHC Cu anodes.Research was carried out in part at beamline X23A2 at the National Synchrotron Light Source, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Division of Materials Sciences and Division of Chemical Sciences. H.S.I. was supported by the U.S. Department of Energy, Division of Materials Sciences, Office of Basic Energy Science under Contract No. DE-AC02-76CH00016

Load sensitive stable current source for complex precision pulsed electroplating

Electrodeposition is a highly versatile and well explored technology. However, it also depends strongly on the experience level of the operator. This experience includes the pretreatment of the sample, and the composition of the electrolyte settings of the plating parameters. Accurate control over the electroplating current is needed especially for the formation of small structures, where pulsed electrodeposition has proven to reduce many unwanted effects. To bring precision into the formation of optimal recipes, a highly flexible current source based on a microcontroller was developed. It allows a large variety of pulse waveforms, as well as maintaining a feedback loop that controls the current and monitors the output voltage, allowing for both galvanostatic (current driven) and potentiostatic (voltage driven) electrodeposition. The system has been implemented with multiple channels, permitting the simultaneous electrodeposition of multiple substrates in parallel. Being based on a microcomputer, the system can be programmed using predefined recipes individually for each channel, or even adapt the recipes during plating. All measurement values are continuously recorded for the purpose of documentation and diagnosis. The current source is based on a high power operational amplifier in a modified Howland current source configuration. This paper describes the functionality of the electrodeposition system, with a focus on the stability of the source current under different electrodeposition current densities and frequencies. The performance and high capability of the system is demonstrated by performing and analyzing two nontrivial plating applications